1. Field of the Invention
The present invention relates to an apparatus and method for forming a honeycomb body.
2. Description of Related Art
Known in the prior art is a method for producing a honeycomb structure, wherein a ceramic material is extruded from a die having a plurality of slits, while a guide ring is provided at a peripheral portion of the die. A flow of the ceramic material from the die is blocked at the guide ring, so that the material issued from the slits is collapsed, thereby providing a skin portion around a core portion in the honeycomb structure.
In order to produce a desired shape of the honeycomb structure, it is essential to desirably control the flow speed of the ceramic material via the die, which is influenced by various factors. In view of this, a Japanese Examined Patent Publication No. 55-36486 discloses an extrusion of a ceramic material by a screw extruder having an outside heating device arranged at a location upstream from a die, so that the ceramic material is subjected to heating by the heater prior to the extrusion from the extruder, so that the ceramic material during the extrusion process is subjected to a uniform state of the heating.
However, the prior art directed to a uniform control of a temperature at the entire part is not sufficient from a view point of control of a desirable control of the flow speed at an entire part of the die. Namely, the desired control of the flow speed is required not only at the core portion but also at the masked peripheral portion. Namely, unmatched flow speed between the core portion and the masked portion causes defects, such as cracks or creases to be generated at a skin portion of the honeycomb structure. In order to obtain such a matched speed at the core and peripheral portion, tiresome work is necessary for an adjustment of the guide ring due to the fact that a flow speed of the ceramic material is influenced by various factors, which increases the production cost.